The present invention relates to a measuring apparatus for measuring specific methanogenic activity of granular sludge used in an anaerobic wastewater processing method.
As a known measuring apparatus for measuring specific methanogenic activity of sludge, there is that used in a method called as xe2x80x9cthe vessel methodxe2x80x9d as disclosed in the publication xe2x80x9cJournal of water and Waste (in Japanese) Vol. 37, No. 7 (1995)xe2x80x9d, which is as shown in FIG. 12 and FIG. 13, and description is made hereinafter for the apparatus. A plurality of narrow-mouthed bottles 62, to each of which a gas conduit piping 61 is disconnectably connected, are placed in water in a thermostatic bath 63 with a stirring member 66 and a heater 67 installed in the thermostatic bath 63, a tip of the gas conduit piping 61 is inserted in a washing gas bottle 68 filled with 1N, NaOH, this washing gas bottle 68 and a gas holder 69 are connected to each other with the gas conduit piping 61, and a scale 72 is attached to the gas holder 69.
An operating sequence when measuring specific methanogenic activity of sludge with the apparatus as described above is shown in an operation flow chart in FIG. 13, and in this flow chart,
(1) A first sludge to be measured is sampled,
(2) the sampled sludge and a reaction mixture are put in the narrow-mouthed bottle 62 placed in the thermostatic bath 63, and is kept in the state for raising the anaerobic characteristics of the apparatus with the stirring member 66 and heater 67 being operated for 12 hours at 35xc2x0 C.,
(3) A gas generated in the narrow-mouthed bottle 62 is guided through the gas conduit piping 61 into the washing gas bottle 68 filled with 1N, NaOH to remove CO2, and then
(4) the gas is kept for 6 to 8 hours in the gas holder 69, and during this period up and down movement of the gas holder 69 is visually read with the scale 72 once for every 1 hour to determine specific methanogenic activity (slope) [gCOD], and finally
(5) gVSS of the sludge is measured for 24 hours.
Then based on the specific methanogenic activity (slope) and a quantity of sludge [gVSS], a quantity of methane gas formed per day [gCOD/gVSS/d] is computed according to a sequence similar to that according to the present invention as described hereinafter.
By the way, with the measuring apparatus as described above, gas phase replacement is not taken into account in the measurement of specific methanogenic activity as described above, and a long period of time is required for raising the anaerobic characteristics of the apparatus. Totally, 44 hours are required for sampling of the sludge, and during this period of time an operator is required to continuously monitor a gauge without leaving the measuring apparatus, which is a heavy work load to the operator. In addition, measurement values are visually read by the operator from the scale, so that the read values may be inaccurate, and further careful operations are required to keep the narrow-mouthed bottle without causing movement thereof. When measuring sludge with a low specific methanogenic activity, sometimes a NaOH aqueous solution may flow in the reverse direction from a gas holder to the narrow-mouthed bottle with the specific methanogenic activity computed manually by the operator, which requires complicated operations and makes it difficult to quickly compute the specific methanogenic activity or to determine whether measured values on the specific methanogenic activity are acceptable or not.
It is an object of the present invention to provide a specific methanogenic activity measuring apparatus, which can solve the problems in the conventional type of specific methanogenic activity measuring apparatus as described above, requires only a short period of time for raising the anaerobic characteristics, finishes all steps from sampling sludge up to measurement, and also which can automatically record a result of measurement without requiring an operator to stay near the measuring apparatus and continuously monitor the gauges, and resultantly, which does not give a large work load to the operator, nor requires the operator to pay minute attentions for statically keeping the reaction vessel, and further, in which the NaOH solution never flows in the reverse direction into the reaction vessel when measuring sludge with low specific methanogenic activity, the operator is not required to manually compute the specific methanogenic activity, the activity can quickly and easily be computed, and further determination can be made as to whether the measured specific methanogenic activity value is acceptable or not.
To achieve the objectives as described above, the invention provides a specific methanogenic activity measuring apparatus having a measuring means for measuring specific methanogenic activity of sludge in anaerobic wastewater or soil processing and a recording means, and the measuring apparatus has a pressure vessel with a cover removably attached thereto, a carbon dioxide gas absorbing container, and a thermostatic bath with the pressure vessel removable placed therein as the measuring means, in which a pressure transducer based on the pressure-electricity converting system connected to the recorder is attached to the cover, a supporting member for the carbon dioxide gas absorbing container is attached to an external bottom surface of the carbon dioxide gas absorbing container, a gas piping for venturation penetrating an internal surface of the container, and further a gas piping with a valve for gas phase replacement to a cover of the pressure vessel respectively, and in the invention, a magnetic stirrer is attached to the internal bottom surface of the pressure vessel.
The inventions provide the advantages that the time required for raising the anaerobic characteristics of the apparatus is short, all steps from sampling sludge up to final measurement can be finished within a short period of time, also the apparatus itself can automatically record a result of measurement, an operator is not required to stay near the apparatus for continuously monitoring the gauges, thus the work load of the operator is reduced, and further, an accurate result of measurement can be obtained, minute attentions are not required for statically keeping the reaction vessel, and the NaOH solution never flows in the reverse direction into the reaction vessel when measuring sludge with a low specific methanogenic activity.
The invention also provides a screen display unit having a computing section for automatically computing a quantity of methane formed per day [gCOD/gVSS/d] from information on pressure detected by a pressure transducer based on a pressure-electricity converting system in the measuring means as a recording means and a display section for displaying a computed value processed by the computing section; wherein the computing section measures changes in pressure for a specified period of time for determination according to a pressure signal from the pressure transducer in the measuring means, converts the slope of the pressure change to a historical change in a quantity of formed gas and also to a unit [gCOD/h] which can be expressed as a load corresponding to a methane gas forming rate per hour x[ml], computes a methane gas forming rate per day for one unit volume of sludge by dividing the converted methane gas forming rate x[gCOD/h] by a total volume of sludge [gVSS] used for measurement; the computing section has an A/D convertor for converting a pressure signal from the pressure transducer in the measuring means to a digital signal, a determination time counter for manually setting a determination time therein and numerically displaying a determination time, a gVSS counter for manually setting a gVSS of sludge therein and numerically displaying the gVSS of the sludge, and a control section for computing a methane forming rate [gCOD/gVSS/d] per day according to the pressure signal from the A/D converter, a determination time from the determination time counter, and a gVSS of the sludge from the gVSS counter, or has, in place of the determination time counter and gVSS counter, a keyboard for entering a determination time and a gVSS for the sludge, a screen display unit for displaying on the screen the determination time and the gVSS of the sludge entered from the keyboard, a timer for counting a determination time inputted from the keyboard, and a memory for storing therein a determination time and a gVSS and enabling the control section to read and fetch data stored therein; and the display section comprises a plurality of lamps used for comparing a value of a methane forming rate [gCOD/gVSS/d] computed by the computing section to a threshold value and displaying a result of comparison by turning ON or OFF discretely, and further, the display section compares the value of methane forming rate [gCOD/gVSS/d] computed to the computing section to a criteria for determination and displays on the screen whether the result is acceptable or not.
In these inventions, a determining unit in the specific methanogenic activity measuring apparatus automatically computes a methane forming rate per day [gCOD/gVSS/d] from information on pressure detected by a pressure transducer based on the pressure-electricity converting system in the measuring means, and displays the computed value. Namely, pressure change during a specified period of time for determination is measured according to a pressure signal from the pressure transducer, and the slope of the pressure change is converted to a historical change in the gas forming rate. Then the value is converted to a value [gCOD/h] which can be expressed as a load corresponding to a methane gas forming rate per hour x[ml]. This converted methane gas forming rate x[gCOD/h] is divided by a total quantity of sludge [gVSS] used for measurement to obtain a methane gas forming rate per day for one unit quantity of sludge for computing a methane forming rate per day [gCOD/gVSS/d], so that an operation is not required to manually compute a methane forming rate and the rate can quickly and easily be computed, and further whether a measured methane forming rate is accepted or not can be determined.
For better understanding of the present invention, detailed description is made hereinafter for embodiments of the present invention with reference to the attached drawings.